Programming language and runtime environment that allows compiled Java programs to run unchanged on most hardware and software platforms
53
votes
8answers
132k views
Can't seem to disable Java Automatic Update
I'm just tweaking out my new Windows 7 laptop and wanted to disable the automatic Java updating (and thus kill the silly jusched.exe background process), but I can't seem to get it to actually turn it ...
25
votes
7answers
28k views
How to determine JAVA_HOME on Debian/Ubuntu?
On Ubuntu it is possible to have multiple JVMs at the same time. The default one is selected with update-alternatives. But this does not set the JAVA_HOME environment variable, due to a debian policy.
...
19
votes
8answers
3k views
Is it a Best Industry practice to restart web servers periodically?
We have a web application (developed by a third party) that runs on Tomcat. We have been getting very bad performance from the application. The application developer is claiming that it is an ...
16
votes
5answers
37k views
Practical maximum open file descriptors (ulimit -n) for a high volume system
We recently began load testing our application and noticed that it ran out of file descriptors after about 24 hours.
We are running RHEL 5 on a Dell 1955:
CPU: 2 x Dual Core 2.66GHz 4MB 5150 / ...
12
votes
4answers
41k views
Where to set java heap options (e.g. -Xmx) for Tomcat 6 under Ubuntu 9.04?
I'm running Tomcat using the tomcat6 package from Ubuntu 9.04, which makes a daemon out of Tomcat using jsvc. I'd like to know the proper way to set Java heap options like -Xmx for Tomcat. I'd like to ...
12
votes
5answers
4k views
I'm designing a system to handle 10000 TCP connections per second, what problems will I run into?
I have a relatively new 8-core box running CentOS. I would like to develop a stats server that uses TCP. It's very simple, it accepts a TCP connection, increments a counter and closes the connection. ...
10
votes
6answers
6k views
Open source tomcat log viewer
I'm managing several tomcat instances (aprox 30-35) and looking for some console to centralize the logs.
I tried php-syslog-ng before (no with tomcat), and found it useful. I would like that these ...
9
votes
4answers
30k views
What is the value of JAVA_HOME for CentOS?
I have install java through yum on CentOS, however another java programme needs to know what the JAVA_HOME environmental variable is. I know all about setting environmental variables, but what do I ...
9
votes
5answers
448 views
How do I find the cause for a huge difference in performance between two identical Ubuntu servers?
I am running two Dell R410 servers in the same rack of a data center (behind a load balancer). Both have the same hardware configuration, run Ubuntu 10.4, have the same packages installed and run the ...
9
votes
1answer
8k views
How can I restrict the java plugin to run only on certain sites in Internet Explorer?
I want to secure our centrally managed computers better and it is very difficult to automatically deploy the java runtime, but how to do that is another question.
I find the security of Java ...
9
votes
2answers
7k views
How do you manage Java in your Windows/Active Directory environment?
Like I suppose a lot of people, we have a Windows/Active Directory environment and a lot of internal line of business apps that require Java. Our experience is that Java does not play nice in such a ...
8
votes
5answers
25k views
Top - what does Virtual memory size mean? …linux/ubuntu
I am running Top to monitor my server performance and 2 of my java processes show virtual memory of upto 800MB-1GB. Is that a bad thing?
What does virtual memory mean? And oh btw, I have swap of 1GB ...
8
votes
4answers
2k views
JVM Memory Consumption
I am trying to run tomcat on a low memory system (150-256Mb). Even though I start the JVM with -Xmx64m (which should be the default anyway), the process immediately takes up 200Mb+.
I wonder why the ...
8
votes
5answers
2k views
Suggestions for free/cheap asset/patch management software (Adobe, Java, etc)
I am using WSUS for Microsoft patching but would like something that will inventory and patch Adobe, Java, Firefox, Quicktime, etc.
I have used Lumension in the past and it was OK but it is too ...
7
votes
2answers
3k views
SSL Certificate Error: certificate_unknown
I want to create push notification server and while installing SSL certificate and .p12 file in server we are facing the below error: I want to know what is the wrong with ssl certificate because I am ...
7
votes
5answers
11k views
Tomcat 6.0 service does not start: java/lang/NoClassDefFoundError
I installed Tomcat on my Windows server but I can't get it to start. I start the service and I see the progress bar, but it fails.
I installed the Java Runtime Environment Version 6 and created ...
7
votes
1answer
727 views
Tomcat: possible to exclude jars during app deployment?
By default, Tomcat prevents webapps from loading several .jars which are part of the Tomcat distribution (eg the servlet and JSP APIs) - is it possible to configure others to also be excluded?
If it ...
7
votes
1answer
8k views
How can I block Java updates, network-wide?
Java is constantly prompting users to upgrade and, when they do, it tries to install all sorts of other things which we must uninstall. Lately it installs a backup program called Carbonite.
We’ve ...
7
votes
1answer
43k views
Differences between classes12.jar, ojdbc14.jar, ojdbc5.jar and ojdbc6.jar
We are planning to upgrade our application servers to a new version of JRun which is carrying with it an upgrade from Java 1.4 to Java 1.6. As part of that, we have been testing various pieces of our ...
6
votes
4answers
976 views
is it possible to install java without the browser plugin?
I need java, but I don't want any browser to be able to access it.
Is it possible to remove the whole applet/browser plugin code?
6
votes
4answers
138 views
Crashing my disk using Java
I have a Java program that must do the following 3 things:
Download a file from a website.
Run the file trough testA and testB (both in java)
Delete the file and save the test results on the disk.
...
6
votes
5answers
3k views
OpenJDK vs. Sun Java6 on Ubuntu
Due to past (bad) experience resulting from the GCJ stuff being provided by default on certain distributions, I've always traditionally installed the official Sun Java package on servers.
On Ubuntu ...
6
votes
8answers
2k views
Deployment and monitoring tools for java/tomcat/linux environment
I'm a developer for many years, but don't have tons of experience in ops, so apology if this is a newbe question.
In my company we run a web service written in Java mainly based on a Tomcat web ...
6
votes
6answers
7k views
How to block access to a file from being served by Tomcat?
We have a few tomcat servers and we just discovered that some files that we don't want public to have access to those files. To exemplify:
Let say we have a folder /var/www/html/ that we are ...
6
votes
4answers
6k views
which JVM is best for Tomcat?
I have Tomcat 6.0 up and running. I went to tweak the memory sizes and realized that I have it running on the Sun JDK 1.6 client JVM. I don't have the Sun server JVM installed:
C:\>java -client ...
6
votes
4answers
5k views
Cannot switch, ssh to specific user: su: cannot set user id: Resource temporarily unavailable?
/var/log/secure:
su: pam_keyinit(su-l:session): Unable to change UID to 500 temporarily
su: pam_keyinit(su-l:session): Unable to change UID to 500 temporarily
su: pam_unix(su-l:session): session ...
6
votes
3answers
4k views
Sending email using SMTP (Gmail) from Hudson CI
How can I set up Hudson CI so that I can send out emails from the server following a build failure? At the moment all I get is the following error:
com.sun.mail.smtp.SMTPSendFailedException: 530 ...
6
votes
2answers
208 views
SSH unresponsive after stopping Tomcat, many ksoftirqd CPU usage
I have a weird issue.
Every time I stop Tomcat, SSH becomes very slow, almost totally unresponsive. It takes a minute or even more for SSH to accept any command. When I finally get Tomcat started ...
6
votes
1answer
1k views
Tomcat Excessive Memory Consumption
I have a fresh server running Ubuntu 11.04 (Natty) (64-bit). I started off by installing openjdk and tomcat6. When the Tomcat server starts up, it immediately uses 480+ MB of memory. This seems way ...
6
votes
1answer
1k views
Tomcat7 PPA for Ubuntu LTS 10.04.2
Does anyone know of a ppa / repo that will install tomcat7. I know I can install from source but I'd rather if possible use a PPA/Repo.
I found a nice one for sun*cough*oracle-java but there does ...
5
votes
7answers
7k views
Run Jar in Background on Linux
I have a jar that runs forever (infinite loop with socket listening thread) and need it to run in the background at all times. An example would be: "java -jar test.jar" How do I do this? Thanks in ...
5
votes
5answers
5k views
How to reliably take Java Heap Dumps?
My team is running into difficulties when trying to take good heap dumps triggered by OutOfMemoryErrors. For specific reasons we are currently taking the dumps with jmap called from a bash script ...
5
votes
3answers
703 views
Scripted install of Sun Java JDK on Ubuntu 9.04
We are trying to script the install of the sun jdk on Ubuntu 9.04 and have it automatically accept the license agreement. I have seen something around the net about creating a file that the package ...
5
votes
4answers
197 views
What issues do you need to check for deploying a java application on linux?
What issues should be specifically checked for when deploying a server application written in Java (without any specific platform dependencies) that was written and tested on Windows.
Two that I know ...
5
votes
3answers
11k views
How to get a linux network log?
We have a java server running in linux at a specific port that accepts persistent connections for thousands and thousands of users. Recently our clients are not able to connect with a time out error. ...
5
votes
5answers
728 views
What configuration changes do you make to a new Tomcat installation?
After installing Tomcat 5 what configuration changes/tweaks do you apply, and why?
Be specific: name what files you edit, what settings you change and why you do it.
Some areas of interest:
...
5
votes
3answers
472 views
Virtualbox HTTP load testing, host CPU overload issues
I'm doing HTTP load testing benchmarks (using Apache Benchmark and Siege) on a small Java EE 1.7.0 / Tomcat 7.0.26 application running on a Debian Squeeze 6.0.4 x64 virtualized with Virtualbox 4.1.8. ...
5
votes
4answers
1k views
Cannot create Java VM on OpenVZ
I'm constantly encountering an error related to Java and certificates on my Ubuntu server running in OpenVZ when installing things from apt-get. I'm pretty sure it has to do with how Java allocates ...
5
votes
6answers
627 views
load balancing in Tomcat
I want to implement the load balancing in tomcat 6.0 so that we can create more than one instance of a tomcat and when any of the instance is down then other instance will run our application. so that ...
4
votes
3answers
320 views
MultiCPU servers - which one can you suggest? [closed]
We want to install a couple of big servers for our customer to run Oracle on one and Java applications on another. Tired with clusters, replications, want to run everything on one big server.
We ...
4
votes
8answers
275 views
What platform do you run your java apps on?
Even though the JVM is cross-platform, there are be differences in
behaviour;
performance;
stability.
Some of them are quite clear, as in the heap size limitation on 32bit. Some of them are not, ...
4
votes
3answers
133 views
Java default JRE parameters on Unix
Is it possible to configure java in unix to always add a JRE parameter whenever java is run?
e.g. -Dcom.sun.management.jmxremote.port=25800
4
votes
3answers
177 views
Why shouldn't I serve my Java webapp directly with Tomcat?
I have heard several times that one should not serve a Java webapp directly to the outside world from the Tomcat server it is running on. Rather, one should have a regular web server in between -- ...
4
votes
4answers
3k views
Glassfish Vs Tomcat (Java app servers)
I am looking at running a java application server on my debian linux webserver, and am looking for a breakdown of the advantages that using either app server would provide me with (or disadvantages). ...
4
votes
2answers
1k views
Why are there so many processes running?
I host several Rails applications on a VPS using Ubuntu 8.04, Nginx, Passenger, Mysql, RVM, so all the usual suspects.
In the last days it was the first time I really had to debug a problem and look ...
4
votes
2answers
797 views
PermGen error in Java, while memory usage seems low
Java application dies from time to time with PermGen space error, but when I look at the
memory usage it seems low from what I can tell.
It is a Tomcat application, plus there is SOLR server running ...
4
votes
2answers
167 views
How refresh log on daily basis?
I am running this tool called yajsw which generates a log file named as wrapper.log.0. What I notice after sometime it becomes too big and I cannot run the zip command too? Can I run a cron job to ...
4
votes
1answer
1k views
Tomcat JMX Monitoring problem with Perm Gen
i've a problem with our jmx monitoring. we monitor the perm gen of some jvms with jmx. but from time to time the name of the mbean changes from "PS Perm Gen" to "Perm Gen" or vice versa. it happens ...
4
votes
2answers
676 views
How does my jre exceed its heap limits?
I have a jvm whose actual memory use is well in excess of the limits with which it's being launched. It's a Sun VM:
root@jira:/opt/atlassian/jira/jre# ./bin/java -version
java version "1.6.0_26"
...
4
votes
1answer
3k views
Alternatives for heapdumps creation with higher performance than jmap?
I have to create heapdumps, which works nice with jmap. My problem is, that jmap takes very long to create the heapdump file. Especially when the heap is getting bigger (> 1GB) it is taking too long.
...
